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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

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SPECIAL PART: VEGETABLE OILS                 393

oils and oils of marine animals give a more or less semi-solid or pasty, coloured
mass.   Drying oils give an orange-yellow or brown liquid product.

Vegetable Oils

By vegetable oils is meant those fatty substances extracted from the
vegetable kingdom and liquid at the ordinary temperature. These oils
are fairly numerous but only relatively few are in common use, these includ-
ing olive, almond, arachis, colza, cottonseed, linseed, sesame and castor
oils, which are treated in detail below. Table XLIV on p. 410 gives the
principal characters of these oils and of the other more important vegetable


From the seeds of Arachis liypogcea. It is pale yellow and has a slight
odour and an agreeable taste. About 15 grams dissolve in 1000 c.c. of
absolute alcohol at 15°.

With Heydenreich's, Brulle's and Hauchecorne's reagents it gives no
appreciable colorations, only a pale pink colour being obtained with the
last in the cold. The other chief physical and chemical characters are given
later in Table XLIV.

Characteristic of arachis oil is its content of arachidic and lignoceric
acids. The detection and, if required, the determination of these acids
serves to identify the oil and to detect its presence (approximately also
the quantity) in mixtures with other oils.

1. Detection and Determination of Arachidic and Lignoceric
Acids.—The most convenient method for this purpose is that of Tortelli
and Ruggeri (see below), which, like various other methods, is based on
the same principle as Renard's older method.1

A preliminary and more rapid examination may be made by the other
two methods described below.

i. TORTELLI AND RUGGERI. 20 grams of the oil are saponified,
the fatty acids separated, and the solid acids extracted from these by means
of the lead salts,2 the operations being carried out exactly as described in
general method 18 (Tortelli and Ruggeri's method). The solid fatty acids
thus obtained are placed in a suitable flask, 100 c.c. of 90% alcohol and a
drop of dilute hydrochloric acid (about normal) being added. The flask
is closed with a stopper through which a thermometer passes into the liquid
and is then heated gently (not above 60°) on a water-bath and carefully

1  Among other methods suggested for the detection of arachis oil mention may be
made of Torrini's modification of Blarez's method (Ann, Lab. Mm. centrale Gabelle,
Vol. VI, p. 513).

2  According to Guarnieri, the preparation of the lead salts may be shortened by
saponifying the oil with a concentrated solution of caustic potash in glycerine and
then precipitating the lead salt with a solution of lead acetate in glycerine (Staz, sper.
agr. ital., 1909, p. 408).be for two minutes, I gram of mercury being then added and dissolved